Push-pull condenser speaker



May 20,4930. I P. E. EDELMAN 1,759,811

' Y PUSH-PULL CONDENSERSPEAKER Filed April 17,- 1929 4 Shets-Sheet 1 I May 20, 1930. V P. EDELMAN PUSH-PULL CONDEN SER SPEAKER I Filed April 17, 1929 4 Sheets-Sheet 2 May 20, 1930. P. E. EDELMAN 1,759,811

PUSH-PULL CONDENSER SPEAKER Filed April 17, 1929 4 Sheets-Sheet 3 I ffizz/i i z a e/79247;;

4 Sheets-Sheet 4 P. E. EDELMAN PULL CONDENSER SPEAKER PUSH- Filed April 17, 1929 May 20, .1930.

. Patented 1a., 20, 1930 I 15mm mama-mum, or OHICA eo, rumors, assmnon. IO Ernnam Ban-nine,- or cnrcaeo, mnmors f roan-run. counnnsnn s'rmm' V anama-1pm 17,1929. Serial in. $55,957."

My present inventionrelates to improve- .ments'in acoustic condenser-speakers, and is more articularly for a pushull condenser repro ucer, though it may a so be used on.

the out ut of a single vacuum tube'amplifier.

structure and circuit connections to operate An 0 ject of this invention is to provide an .improved acoustic condenser and a method of making the same. ,1

Another ob'ect is p to provide improved a condenser type reproducer from a vacuum tube amplifier source, particularly of the push-pull type with good quality and fidelity of reproduction, including the full range of musical tones and overtones with well defined brilliancy." I

These and other objects, as will presently appear, are accomplished by this invention which is fully described in the following specification andv shown in the accompanying drawings, in .which-' I Figure 1 is a front elevation of-the pushpull type condenser speaker embodying this invention;

Fig. 2 is .an operating circuit diagram therefor;. a v

Fig. 3 is a diagram of a harness unit con nectorfor -9p8ratingthe speaker of Fig. 1

without'i change in regular wiring assembly of a-stand'ard radio set already in use;

Fig. 4 is a section of a construction for the condenser diaphragms used in Fig. 1;

Fig. 5--is a partial section showing a modification offFig.'4;

- Fig. 6 isa plan-view ofa perforated strip used in. the structure of Fig.4;

Fig.7 is a sectional end of Fig. 6 5

Fig. 8 1s a plan view of stri s shown in Fig. 6; v

. 1g. 9 is a plan view of a modificationof Fig.8;and

v i 10 is a artial sectional view of a mod! cation of ig. 4.

Referring to Fig. 1, a stretcher frame 1 car: ries a dielectric diaphragm 7 upon which two separate flexible metal foil electrodes 2, 3 are mounted, separated by a gap 14 on the insulating sheet 7. The electrode 4 has end amodified use of reinforcing strips of soft-lead 4, 4- pasted.

view of the strip thereon with mucilage, or otherwise secured thereon in electrical contact. The electrode 3 "consists of thin metal foil strips .8, 8, 8

rolled over varnished dielectric sheet -7 while ,said varnish is stillwet, and overlapped at rib portions 6, 6.

The electrode 2 is similarly constructed with metal foil strips of aluminum or tin 9., 9., 9, smoothed over avarnished surface of v I dielectric sheet 7. Japan gold size is a suitable varnish to use for'this purpose, because 'of its conductingqualities. Metal foil 9 is overlapped at rib portions 11, 11. A gap 14 separates electrode=3 from electrode 2. Also, a mar in is left bare at 13around the dielectric dlaphragm sheet 7. A tinsel connector strip 15 contacts with end metal ribbon 4 to serve as a terminal for electrode 3.v A similar terminal 10 is fastened to the strip 5 of electrode 2, at 16. The co-operating flexible electrode diaphragm at rear side of dielectric diaphragm'7'will presently be discussed after referring first to circuit connections of-Figs.

2 and 3, in order that the purpose of the double electrodes 2, 3 may be made clear.

In- Fig. 2, a push-pull type vacuum tube amplifier 25 has an input 23 which may be connected to a radio set or other'electrical sound unit, and an output choke coil 24. The two amplifier vacuum tubes 21, 22 are connected to the coil 24 in a customary manner. Power unit 20 supplies energizing current'to the amplifier 25 when the plug. 19 is connected to a source of. electric current. A polarizing power unit-18 supplies about 300 volts of direct potential to polarize the acoustic condenser 17. The positive terminal of unit 18 connects to the filaments of vacuum tubes:

21 and 22. The flexible condenser electrode 37 co-operates with the diaphragm 7, and is connected tothe negative pole of the unit 18.

' 4. One of the double electrodes on the dia: phragm. 7, namely electrode 3, connectsv tothe plate of vacuum tube 21,'while electrode. 2 also carried by diaphragm 7 connects to the plate of vacuum tu e-22.- A by-pass condenser 26 of 1 mid. capacity is shunted across the .polarizer. power unit 18. Unit 18 is provided with an energizing plug connector 19 for attachment to a current supply source.'

.This combination is suitable for use on a push-pull amplifier already in service with- I out necessitatlng wiring changes. A suitable harness unit for this purpose 1s adapter plugs 34, to the two'condenser electrodes 2, 3, carried Ondiaphragm 7 of condenser 17. \Vire 28 extends from the negative terminal of the polarizer power unit 18 through the cable 27 to the flexible electrode 37 of the acoustic condenser v17. I y

The" vacuum tubes, 21, 22 of Fig. 2 are inserted in connector plugs 34, 35 respective- 1y before use so as to obtain the auxiliary connections aforesaid through the cable 36. Radio sets having push-pull type amplifiers made for low voltage transformer output can thereby be operated with the condenserspeaker 17 without requiring a new high voltage output transformer therein.

Referring to Fig. 4, the flexible diaphragm-- electrode ,37 is permeable to air flow, and conslsts of a metal tinsel cloth 37 reinforced with cross-connector narrow lead. foil strips 39,

which have perforations 45, as shown in Fig.

6. The diaphragm dielectric sheet 7 1s spaced from the flexible electrode 37 by a thin air gap 40, and a portion of one of the electrodes '2 carried on diaphragm 7 is shown as a thin metal cloth 41 fastened thereto,

' The lead, aluminum, or other metal strips as 39 are preferably secured to the metal tinsel cloth by soldering or welding. Thus solder 39 may be applied to the back of the metal strip (Fig. 7 and this is then pressed firmly against the tinsel cloth by a hot soldering iron or a hot roll, when the solder will unite the cloth firmly to thestrip. Strips of thin solder the width of the metal strip 37 may also be used.

A modified structure is shown in Fig. 5.

An extra fabric 42, such as linen crash, carries electrode 37 loosely separated therefrom by air gap 43. Flexible electrode 37 has the same structure as in Fig. 4, with tinsel cloth 38 reinforced by narrow perforated lead strips 39.

Dielectric diaphragm 7 carries the electrode 2, and is separated from the electrode 39 by a tiny air gap 40. The fabric 42 is permeable to'a-ir but rest-ricts'the anz'plitude of vibration of the diaphragm elect ode 37,

thereby softening therefrom. 1 y

Referring to Figs. 6 and 7, the soft lead ribbon strip 39; has a plurality of perforations 45 permitting air to flow'therethrou h As shown in Fig. 8, lengihigh pitched tone response Wise perforated strips 44, 44 and crosswise disposed perforated strips 47 may be supported on a fabric sheet 47 to serve as a 'flexible diaphragm electrode in lieu of the tinsel .cloth 38 used for electrode 37 of Fig. 4.

' The metal strips 39 may be spaced closer together at the center of the frame, thereby causing the center to respond more readily to notes of low pitch, while the side areas respond better to high pitch notes. This result is also obtained by using strips of different widths, different thicknesses, different spacings, and different materials.

A further modified construction for electrode member 37 is shown in Fig. 9. No supporting fabric is used,"b1'1t instead a special tinsel cloth is, woven-with fine tinsel cross threads 48,; and-"wider tinsel strands 49,

lengthwise interposed with strengthening fabric threads 50.

A modified structure for the dielectricdiaphragm assembly is shown in Fig. 10, where the empire cloth sheet 7 has a varnish size layer 52 on which aluminum foil 2, prepared with a rou hened or electrolytic dielectric film formecf surf'ace 51, is caused to'adhere.

The tinsel cloth maybe made of either flat or crinkled tinsel strands as disclosed in my earlier application, Serial No. 354,233, filed April 11, 1929, the crinkled tinsel cloth giving a more effective response, probably be- 7 cause of the greater working area.

While I have. shown and described but a few embodiments of my invention, itis to be understood'that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made which do not depart from the spirit and scope of the invention as disclosed in the appended claims. Y

I claim:

1. In an acoustic condenser having electrodes and a co-operating dielectric sheet therefor, the improvement which comprises attaching perforated soft metal strips to'one of said relectrodes to control the vibrations] thereof.

flexible perforated soft metal electrode, a dielectric diaphragmadjacent thereto, and a co-operating flexible electrode carried on said diaphragm.

3. An acoustic condenser comprising a flexible perforated lead foil electrode, a second flexible foil electrode, and a dielectric sheet placed between said electrodes.

4. n acoustic condenser comprising a dielectric dlaphragm, an electrode carried thereon, and a co-operating electrode therefor comprlsing a flexible woven'fnetal cloth having a plurality of'combinedco'nnector and vilp'lation controlling strips combined there- W1 Y 2. An acoustic condenser consisting of a.

5. An acoustic condenser comprising a .lexible electrode permeable to the flow of air carried by'said sheet, a dielectric diaphragm mounted adjacent to said electrode, and an electrode coatin carried by said diaphragm, whereby said abric sheet assists in controllmg the vibrations of said -flexible electrode carried thereon.

6. An acoustic condenser comprising two flexible electrodes, one of which is permeable to air flow while the other is not, and a dielectric diaphragm therebetween.

7 An acoustic condenser comprising electrodes, and a co-operating dielectric diaphragm therefor, one of said electrodes comprising'a crinkled metal tinsel cloth.

8. An acoustic condenser comprising electrodes, and a co-operating dielectric diaphragm therefor, one of said electrodes'com prising a woven metal fabric.

9. In an acoustic condenser having a dielectric diaphragm and co-operating electrodes therefor, means to fasten one of said electrodes to said diaphragm consisting of a varnish size coated on said diaphragm, char;

.acterized by the fact that one surface of said last named electrode is roughened toincrease the area thereof exposed to the adhesion of said varnish size. I

10. An acoustic condenser comprising a flexible electrode permeable ,to the flow of air, a co-operati-ng diaphragm therefor, and

. a second electrode carried on said diaphragm and having a wrinkled surface to increase the'eifectlve area thereof.

11. An acoustic condenser comprlsing an electrode permeable to air, a dielectric diangm placed adjacent thereto, and an electrode having a roughened film surface there-'- on carried by said diaphragm.

12. An acoustic condenser comprisingan electrode permeable to air flow, a dielectric diaphragm adjacent thereto, and a plurality of separate electrodes carried by said diaphragm.

13. An acoustic condenser foroperation on a push-pull amplifier output comprising an electrode permeable to air flow, a dielectric diaphragm placed close thereto, and two sepa-rate and insulated electrodes carried on said diaphragm;

14. An acousti condenser comprising. a

ered or welded 17,. An acoustic condenser comprising a frame carrying two electrodes, and a dielectric therebetween, one of which electrodes comprisesspaced metal strips of unequal Weight secured at their ends to said frame.

18. An acoustic condenser having two electrodes, and a dielectric therebetween, one of said electrodes comprising a metal tinsel cloth and metal strips fastened and electrif cally. connected thereto at spaced distances on said cloth.

19. An acoustic condenser comprising a flexible air permeable electrode, a dielectric diaphragm spaced adjacent thereto, a flex ible electrode carried on said-diaphragm, and

a fabric. cloth stretched adjacent to said air permeable electrode to dampen the'vibra-tions thereof. g

20. An acoustic condenser comprising'an electrode permeableto air' flow a dielectric diaphragm adjacent thereto, an electrode carried by said diaphragm, and a plurality of flexible strips on the airpermeable electrode disposed to contact-with spaced areas of said diaphragm to control the air moved when said diaphragm is vibrated.

In testimony whereof, I have hereunto set my hand andaifixed my seal thisl1 2th day of April,

PHILIP E. EDELMAN. 

